Liquid crystal display panel

ABSTRACT

A liquid crystal display panel is provided and includes a pair of substrates arranged face to face so as to sandwich a liquid crystal layer, a lower electrode formed on a lower substrate, an upper electrode formed on the lower substrate through an insulating layer, in which plural slits are formed in each sub-pixel, wherein each of the plural slits is formed as an aperture in which both ends thereof in the longitudinal direction are closed, and an alignment film formed so as to cover a surface of the upper electrode and the insulating layer. The plural slits have different widths at both ends of slits in a longitudinal direction, and a rubbing direction of the alignment film is a direction crossing longitudinal edges of each of the slits.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/327,772, filed Jul. 10, 2014, which application is acontinuation of U.S. patent application Ser. No. 12/976,365, filed Dec.22, 2010, issued as U.S. Pat. No. 8,804,084 on Aug. 12, 2014, whichapplication references Japanese Priority Patent Application JP2008-161380 filed in the Japan Patent Office on Jun. 20, 2008, theentire content of which is hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a horizontal-electric field liquidcrystal display panel. More specifically, the invention relates to aFringe-Field-Switching (referred to as “FFS” in the followingdescription)-mode liquid crystal display panel with good viewing-anglecharacteristics and with less coloring.

As the liquid crystal display is characterized in that it is light inweight, thin, and has low power consumption as compared with a CRT(cathode ray tube), it is used for many electronic apparatus fordisplay. The liquid crystal display panel changes orientation of liquidcrystal molecules by an electric field, which are aligned in a givendirection by performing rubbing processing to an alignment film, andchanges the transmission amount or the reflection amount of light todisplay images.

As methods for applying an electric field on a liquid crystal layer ofthe liquid crystal display panel, there are a vertical-electric fieldtype and a horizontal-electric field type. In a vertical-electric fieldliquid crystal display panel, an electric field of a nearly verticaldirection is applied to liquid crystal molecules by a pair of electrodesarranged so as to sandwich the liquid crystal layer. As thevertical-electric field liquid crystal display panels, a TN (TwistedNematic) mode, a VA (Vertical Alignment) mode, a MVA (Multi-domainVertical Alignment) mode and the like are known. In ahorizontal-electric field liquid crystal display panel, a pair ofelectrodes are provided so as to be insulated from each other on aninner surface of one of a pair of substrates arranged to sandwich theliquid crystal layer and an electric field of a nearly horizontaldirection is applied to liquid crystal molecules. As thehorizontal-electric field liquid crystal display panels, an (In-PlaneSwitching) mode in which the pair of electrodes do not overlap in planview and an FFS (Fringe Field Switching) mode in which the pair ofelectrodes overlap are known.

Among the above modes, in the FFS-mode liquid crystal display panel, apair of electrodes including an upper electrode and a lower electrodeare arranged at different layers respectively through an insulatingfilm, slit-shaped openings are provided at the upper electrode and theelectric field in the nearly horizontal direction passing through theslits is applied to the liquid crystal layer. The FFS-mode liquidcrystal display panel is widely used in recent years because it hasadvantages such that wide viewing angle can be obtained as well as imagecontrast can be improved. However, a slit having a fixed width is usedin each sub-pixel in the horizontal-electric field liquid crystaldisplay panel, therefore, there are a problem that coloring occursdepending on a viewing angle direction due to VT characteristics inrespective sub-pixels. In order to improve the viewing anglecharacteristics and to reduce the coloring in the horizontal-electricfield liquid crystal display panel, attempts to divide a rubbingdirection into plural directions in one pixel have been made (refer toJP-A-2005-196118 (Patent Document 1)). Here, the liquid crystal displaypanel disclosed in Patent Document 1 will be explained in reference toFIG. 10.

FIG. 10 is a schematic plan view of one sub-pixel of thehorizontal-electric field liquid crystal display panel disclosed inJP-A-2005-196118 (Patent Document 1).

In a horizontal-electric field liquid crystal display 50, one sub-pixelis divided into four domains of IA, IIA, IIIB, and IVB, and angles madeby common electrodes 51 a, 51 b as well as pixel electrodes 52 a, 52 bdriven by a TFT and rubbing directions are changed in respectivedomains. In the liquid crystal display panel 50, the four domains areformed by arranging the common electrodes 51 a, 51 b and the pixelelectrodes 52 a, 52 b so as to be folded in the horizontal direction andthe vertical direction respectively, the rubbing direction is changed ina region A and a region B of one sub-pixel, and further, colorconversion is compensated with one another in respective domains toreduce the coloring.

SUMMARY

According to the liquid crystal display panel 50 in related art, theimprovement of viewing angel characteristics and the reduction of thecoloring can be expected after a sort. However, in the case of the aboveliquid crystal display panel 50, there is technical difficulty that itis necessary to divide the rubbing direction into plural directionswithin a narrow region of one sub-pixel. Moreover, as four multi-domainsare formed by slits having a fixed width in the above liquid crystaldisplay panel 50, four regions are generated in one sub-pixel, whichcauses a problem that it is difficult to obtain good displaycharacteristics due to disclination.

Thus, it is desirable to provide an FFS-mode liquid crystal displaypanel with good viewing angle characteristics and with less coloring.

According to an embodiment, there is provided a liquid crystal displaypanel having a pair of substrates arranged face to face so as tosandwich a liquid crystal layer including a lower electrode, an upperelectrode formed on a surface of the lower substrate through aninsulating layer, in which plural slits are formed in each sub-pixel andan alignment film formed so as to cover a surface of the upper electrodeand the insulating layer on one of the pair of substrates, in which theplural slits have different widths at both ends of slits in alongitudinal direction.

The liquid crystal display panel according to the embodiment has a pairof substrates arranged face to face so as to sandwich the liquid crystallayer and includes the lower electrode, the upper electrode formed onthe surface of the lower substrate through the insulating layer, inwhich plural slits are formed in each sub-pixel and the alignment filmformed so as to cover the surface of the upper electrode and theinsulating layer on one of the pair of substrates. The liquid crystaldisplay panel according to the embodiment operates in an FFS mode by theabove structure. In the liquid crystal display panel of the embodiment,the lower electrode may be formed on a surface of an interlayer filmmade of a resin film or may be formed on a surface of transparentsubstrate such as a glass substrate. As the insulating film formed onthe surface of the lower electrode, an inorganic insulating film such assilicon dioxide or silicon nitride is used, and preferably siliconnitride is used from a viewpoint of insulation performance. As the upperelectrode and the lower electrode, a transparent conductive materialsuch as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) can be used.

The light transmittance of the liquid crystal display panel vanesaccording to variation of drive voltage applied to the liquid crystallayer. The characteristics are called voltage transmittance (VT)characteristics. The variation of the light transmittance due tovariation of the drive voltage differs according to a light wavelength,therefore, a phenomenon called coloring occurs. In the case of theFFS-mode liquid crystal display, the relation between the voltageapplied to the liquid crystal layer and light transmittance of theliquid crystal layer, namely, the VT characteristics vary according toangles made by the slits of the upper electrode in the longitudinaldirection which cross the rubbing direction and the rubbing direction.

The liquid crystal display panel according to the embodiment has thestructure in which plural slits have different widths at both ends ofslits in the longitudinal direction. When such structure is applied, theangles made by edges of both sides of each slit along the longitudinaldirection and the rubbing direction vary. Moreover, the widths of theslit and an electrode portion between the slits sequentially vary alongthe longitudinal direction, therefore, the VT characteristics areshifted at portions of respective widths, as a result, different pluralVT characteristics can be obtained in each slit. When plural VTcharacteristics are included in each slit, the plural VT characteristicsare superimposed and VT characteristics represented by an envelopethereof can be obtained.

Accordingly, the VT characteristics in a wide range are included in theliquid crystal display panel according to the embodiment, therefore, theliquid crystal display panel in which viewing-angle characteristicsbecome good as well as coloring hardly occurs can be obtained. The pixelhaving plural slit widths can be obtained according to the structure,therefore, plural VT characteristics can be obtained.

In the liquid crystal display panel of the embodiment, it is preferablethat each of the plural slits has a slit opening in which both endsthereof in the longitudinal direction are closed.

As both ends of the plural slit opening in the longitudinal directionare closed in the liquid crystal display panel according to theembodiment, the shape of the end of the slit can be formed precisely,therefore, reverse twisted domain hardly occurs and the high-qualityliquid crystal display panel can be provided.

In the liquid crystal display panel of the embodiment, it is preferablethat edges of the slit along the longitudinal direction are formed to beasymmetrical with respect to an axis corresponding to the longitudinaldirection of the slit.

When the edges of the slit along the longitudinal direction areasymmetrical with respect to the axis corresponding to the longitudinaldirection of the slit, angles made by edges of both sides of each slitalong the longitudinal direction and the rubbing direction differ.Additionally, the angles made by edges of both edges of each slit alongthe longitudinal direction and the rubbing direction can be set tooptional plural values, therefore, plural VT characteristics fixed bythese angles can be optionally set. Accordingly, the liquid crystaldisplay panel in which viewing-angle characteristics become good as wellas the coloring further hardly occurs can be obtained according to theembodiment.

In the liquid crystal display panel of the embodiment, it is preferablethat the slit has a folding portion at which edges of the slit along thelongitudinal direction of the slit are folded in a direction in whichthe edges are apart from each other.

When the slit has the folding portion at which the edges of the slitalong the longitudinal direction of the slit are folded in the directionin which the edges are apart from each other, angles made by edges atboth sides of each slit in the longitudinal direction and the rubbingdirection will be at least three kinds. Accordingly, at least threekinds of VT characteristics are obtained in each slit in the liquidcrystal display panel according to the embodiment, therefore, the liquidcrystal display panel in which viewing-angle characteristics become goodas well as the coloring further hardly occurs can be obtained accordingto the embodiment.

In the liquid crystal display panel of the embodiment, it is preferablethat plural pairs of slits are included, in which slits in each pairhave different shapes respectively.

Each pair of slits having different shapes has at least two kinds of VTcharacteristics in each pair of slits which are different according tothe shape of respective slits. Therefore, the liquid crystal displaypanel in which viewing-angle characteristics become good as well as thecoloring hardly occurs can be obtained according to the embodiment. Asmore slits can be arranged, the transmittance is improved.

In the liquid crystal display panel of the embodiment, it is preferablethat the slits in each pair having the same shape are arranged to beinverted with respect to each other at a central axis in the directionorthogonal to the longitudinal direction of the slits.

When slits in each pair having the same shape are arranged to beinverted with respect to each other at a central axis in the directionorthogonal to the longitudinal direction of the slits, many pairs ofslits having different shapes from each other can be arrangedsymmetrically with respect to the axis within one sub-pixel. Whenapplying such structure, at least two kinds of VT characteristics areobtained in each pair of slits as well as many slits can be arranged inone sub-pixel, in addition, a light emitting state of liquid crystalwill be symmetrical with respect to the central axis in the directionorthogonal to the longitudinal direction of the slits. Accordingly, theliquid crystal display panel in which viewing-angle characteristicsbecome good, an aperture ratio is high, display quality is good, andfurther, the coloring hardly occurs can be obtained according to theembodiment.

In the liquid crystal display panel of the embodiment, it is preferablethat the slits in each pair having different shapes are arranged to beinverted with respect to each other at a central axis in the directionorthogonal to the longitudinal direction of the slits.

When slits in each pair having different shapes are arranged to beinverted with respect to each other at a central axis in the directionorthogonal to the longitudinal direction of the slits, many pairs ofslits having different shapes from each other can be arrangedsymmetrically with respect to the axis within one sub-pixel. Whenapplying such structure, at least three kinds of VT characteristics areobtained in each pair of slits as well as many slits can be arranged inone sub-pixel, in addition, the light emitting state of liquid crystalwill be symmetrical with respect to the central axis in the directionorthogonal to the longitudinal direction of the slits. For example, inthe case that respective edges forming one slit are not formed to beparallel to each other, four kinds of VT characteristics can beobtained. Accordingly, the liquid crystal display panel in whichviewing-angle characteristics become good, display quality is good aswell as the coloring hardly occurs can be obtained according to theembodiment.

In the liquid crystal display panel of the embodiment, it is preferablethat the slits in each pair are formed so that edges of adjacent slitsalong the longitudinal direction are parallel to each other.

When the edges of adjacent slits along the longitudinal direction areformed to be parallel to each other, slits in each pair have shapescomplementary to each other. When applying such structure, slits whichare asymmetrical to each other with respect to the central axis in thedirection orthogonal to the longitudinal direction of the slits, and atleast two to four kinds of VT characteristics are obtained in each pairof slits as well as many pair of slits in which slits in each pair havedifferent shapes are efficiently arranged in one sub-pixel. Accordingly,in the liquid crystal display in which viewing-angle characteristicsbecome good, transmittance is high as well as the coloring hardly occurscan be obtained according to the embodiment.

In the liquid crystal display panel of the embodiment, it is preferablethat a rubbing direction of the alignment layer is a direction crossingall edges corresponding to the longitudinal direction of the slits.

According to the liquid crystal display having the embodiment, fringefield effect can be exerted in all edges corresponding to thelongitudinal direction of the slits, therefore, advantages can beachieved more noticeably.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view for explaining the operationprinciple of a liquid crystal display according to an embodiment;

FIG. 2A is a plan view of an upper electrode of one pixel according to afirst embodiment and FIG. 2B is an enlarged view for explaining anglesmade by one slit and a rubbing direction of FIG. 2A;

FIG. 3 is a graph showing VT curves of long edges of the slit accordingto the first embodiment;

FIG. 4A is a plan view of an upper electrode of one pixel according to asecond embodiment and FIG. 4B is an enlarged view for explaining anglesmade by one slit and the rubbing direction of FIG. 4A;

FIG. 5A is a plan view of an upper electrode of one pixel according to athird embodiment and FIG. 5B is an enlarged view for explaining anglesmade by one slit and the rubbing direction of FIG. 5A;

FIG. 6 is a graph showing VT curves of long edges of the slit accordingto the third embodiment;

FIG. 7A is a plan view of an upper electrode of one pixel according to afourth embodiment and FIG. 7B is an enlarged view for explaining anglesmade by a pair of slits and the rubbing direction of FIG. 7A;

FIG. 8 A is a plan view of an upper electrode of one pixel according toa fifth embodiment and FIG. 8B is an enlarged view for explaining anglesmade by a pair of slits and the rubbing direction of FIG. 8 A;

FIG. 9 is a graph showing VT curves of long edges of the slit accordingto the fifth embodiment; and

FIG. 10 is a schematic plan view showing arrangement of electrodes andrubbing directions in one sub-pixel of a horizontal-electric fieldliquid crystal display panel in related art.

DETAILED DESCRIPTION

Hereinafter, embodiments will be explained with reference to thedrawings. In respective drawings used for explanation in thespecification, respective layers and respective members are displayedwith different scale ratios in order to allow respective layers andrespective members to be sizes recognizable on the drawings, therefore,they are not displayed with the size corresponding to actual sizes.

FIG. 1 is a schematic cross-sectional view for explaining the operationprinciple of a liquid crystal display panel according to an embodiment.FIG. 2A is a plan view of an upper electrode of one pixel according to afirst embodiment and FIG. 2B is an enlarged view for explaining anglesmade by one slit and a rubbing direction of FIG. 2A. FIG. 3 is a graphshowing VT characteristics of long edges of the slit according to thefirst embodiment. FIG. 4A is a plan view of an upper electrode of onepixel according to a second embodiment and FIG. 4B is an enlarged viewfor explaining angles made by one slit and the rubbing direction of FIG.4A. FIG. 5A is a plan view of an upper electrode of one pixel accordingto a third embodiment and FIG. 5B an enlarged view for explaining anglesmade by one slit and the rubbing direction of FIG. 5A. FIG. 6 is a graphshowing VT characteristics of long edges of the slit according to thethird embodiment. FIG. 7A is a plan view of an upper electrode of onepixel according to a fourth embodiment and FIG. 7B is an enlarged viewfor explaining angles made by a pair of slits and the rubbing directionof FIG. 7A. FIG. 8A is a plan view of an upper electrode of one pixelaccording to a fifth embodiment and FIG. 8B is an enlarged view forexplaining angles made by a pair of slits and the rubbing direction ofFIG. 8A. FIG. 9 is a graph showing VT characteristics of long edges ofthe slit according to the fifth embodiment.

First, the operation principle of an FFS-mode liquid crystal displaypanel common to respective embodiments will be explained with referenceto FIG. 1. An FFS-mode liquid crystal display device 10 includes anarray substrate AR and a color filter substrate CF. In the arraysubstrate AR, plural scanning lines and common wiring are respectivelyprovided in parallel to a surface of a first transparent substrate 11and plural signal lines (all lines are not shown) are provided in adirection crossing these scanning lines and the common wiring. A lowerelectrode 15 made of a transparent material such as ITO, IZO or the likeconnected to the common wiring so as to cover respective regionssectioned by the scanning lines and the signal lines is provided.Therefore, the lower electrode 15 operates as a common electrode. On asurface of the lower electrode 15, upper electrodes 18 made of atransparent material such as ITO in which plural slits 17 are formed ina stripe shape are provided through an insulating film 16. The surfaceof the upper electrodes 18 and the plural slits 17 are covered with analignment layer 20. The upper electrodes 18 are connected to switchingelements such as not-shown TFTs (Thin Film Transistors) and operate aspixel electrodes.

The color filter substrate CF has a structure in which a color filterlayer 23, an overcoat layer 24 and an alignment film 25 are provided ona surface of a second transparent substrate 22. The array substrate ARis placed so as to face the color filter substrate CF to allow the upperelectrodes 18 and the lower electrode 15 of the array substrate AR toface the color filter layer 23 of the color filter substrate CF. Next,liquid crystal LC is sealed between the array substrate AR and the colorfilter substrate CF as well as polarizing plates 26, 27 are arrangedoutside both substrates AR, CF respectively to thereby form the FFS-modeliquid crystal display device 10.

In the FFS-mode liquid crystal display device 10, when the electricfield is formed between the upper electrode 18 and the lower electrode15, the electrode field is directed to the lower electrode 15 at bothsides of the upper electrodes 18 as shown in FIG. 1. Accordingly, it ispossible to drive not only liquid crystal existing in the slit 17 butalso liquid crystal existing on the upper electrodes 18. Therefore, theFFS-mode liquid crystal display device 10 has characteristics that ithas a wide viewing angle as well as high contrast, further, it canperform bright display because of high transmittance. Additionally,there is an advantage that the FFS-mode liquid crystal display device 10generates high storage capacitance collaterally because the overlappingarea of the upper electrodes 18 and the lower electrode 15 in plan viewis large, which eliminates the need for an auxiliary capacitance lineseparately.

First Embodiment

A structure of an upper electrode 18 a of one sub-pixel in the liquidcrystal display panel 10A in the first embodiment will be explained withreference to FIGS. 2A and 2B. The upper electrode 18 a has a rectangularshape, which is depicted in landscape in FIG. 2A. In the upper electrode18 a, plural slits 17 a having the same shape are formed. The slit 17 ais substantially longer than is wide, in which opposite short edges arecalled a first short edge 31, a second short edge 32, and in which afirst long edge is called a long edge 33 and a right long edge is calleda second long edge 34 in a pair of long edges connecting to the shortedges. The first and second long edges 33, 34 of the slit 17 a and arubbing direction R (which is equal to an alignment direction of liquidcrystal when the electric field is not applied) cross each other. Whenan angle made by the left long edge 33 and the rubbing direction R is θ1and an angle made by the right long edge 34 and the rubbing direction Ris θ2 as shown in FIG. 2B, angles made by the first and second longedges 33, 34 of the slit 17 a and the rubbing direction R are arrangedto be θ1≠θ2. Additionally, the slit 17 a is made to be symmetrical withrespect to a central axis Ya in a long edge direction. That is, when aperpendicular bisector of the second short edge 32 of the slit 17 a isthe central axis Ya and lengths of portions of the first short edge 31positioned at both sides of the central axis Ya are respectively X1 andX2, the relation of X1=X2 is satisfied.

In the FFS-mode liquid crystal display panel, the VT characteristicsvary according to the angle made by the long edge of the slit and therubbing direction, the width of the slit and the distance betweenadjacent slits. Accordingly, one slit 17 a of the upper electrode 18 awill have both VT characteristics by the left long edge 33 (displayed asθ1) and VT characteristics by the right long edge 34 (displayed as θ2)as shown in FIG. 3. Accordingly, the liquid crystal display panel 10Aaccording to the first embodiment is observed by an observer as thepanel which has VT characteristics represented by an envelope of both VTcharacteristics as shown in FIG. 3. If a tinge of yellow is added inrespective VT characteristics, the color is compensated with one anotherin respective characteristics such that, when some region has a tinge ofyellow, yellow does not appear in other regions of VT characteristics,as a result, coloring phenomenon can be suppressed.

In the above case, the left edge and the right edge of the slit inclineto the same side with respect to the rubbing direction to make crossingangles as shown in FIGS. 2A and 2B, however, the left edge and the rightedge may incline to the reverse side with respect to the rubbingdirection as the embodiment. In that case, a rotating direction ofliquid crystal differs in the vicinity of the left edge and in thevicinity of the right edge, therefore, large effect can be obtained oncompensation for color variations depending on the viewing angle, inaddition to the effect of color compensation by different VTcharacteristics as in the embodiment. Also in the following embodiments,the same effect can be obtained by setting the rubbing angle in the samemanner.

Second Embodiment

A structure of an upper electrode 18 b of one sub-pixel in the liquidcrystal display panel 10B in the second embodiment will be explainedwith reference to FIGS. 4A and 4B. In FIGS. 4A and 4B, the samereference numerals and signs are given to the same components as theliquid crystal display panel 10A according to the first embodiment andthe detailed explanation thereof is omitted. The upper electrode 18 b isthe same as in the case of the liquid crystal display panel 10Aaccording to the first embodiment in a point that angles made by thefirst and second long edges 33, 34 of a slit 17 b and the rubbingdirection R are arranged to be θ1≠θ2 when the angle made by the leftlong edge 33 and the rubbing direction R is θ1 and the angle made by theright long edge 34 and the rubbing direction R is θ2 as shown in FIG.4B. However, the slit 17 b of the upper electrode 18 b has a differentstructure from the case of the liquid crystal display panel 10Aaccording to the first embodiment in a point that the slit 17 b isformed to be asymmetrical with respect to a central axis Yb in the longedge direction.

That is, when a perpendicular bisector of the second short edge 32 ofthe slit 17 b is the central axis Yb and lengths of portions positionedat both sides of the central axis Yb of the first short edge 31 arerespectively XI and X2, the relation of θ1≠θ2 is satisfied. According tothe structure, respective angles 81, 82 made by the long edges 33, 34 atboth sides of the slit 17 b along the longitudinal direction and therubbing direction R can be set to be optional plural values, therefore,plural VT characteristics fixed by these angles can be optionally set.The VT characteristics having a similar tendency as the upper electrode18 a in the liquid crystal display panel 10A of the first embodiment canbe obtained also by applying the above structure. Accordingly, the sameeffect as the liquid crystal display panel 10A according to the firstembodiment can be obtained also in the liquid crystal display panel 10Baccording to the second embodiment.

Third Embodiment

A structure of an upper electrode 18 c of one sub-pixel in the liquidcrystal display panel 10C in the third embodiment will be explained withreference to FIGS. 5A and 5B. In FIGS. 5A and 5B, the same referencenumerals and signs are given to the same components as the liquidcrystal display panel 10A according to the first embodiment and thedetailed explanation thereof is omitted. A slit 17 c formed in the upperelectrode 18 c has a portion in which the long edges 33, 34 of bothsides in the longitudinal direction are parallel to each other or aportion in which the long edges 33, 34 extend in different directions,which is formed to be symmetrical with respect to a central axis Yc inthe long edge direction. When such structure is applied, respective longedges 33, 34 cross the rubbing direction at three different angles ofθ1, θ2 and θ3 as shown in FIG. 5B. As a result, the liquid crystaldisplay panel 10C of the third embodiment is observed by an observer asthe panel which has the VT characteristics represented by an envelope ofthree VT characteristics as shown in FIG. 6. If a tinge of yellow isadded in respective VT characteristics, the color is compensated withone another in respective characteristics such that, when some regionhas a tinge of yellow, yellow does not appear in other regions of VTcharacteristics, as a result, coloring phenomenon can be moresuppressed.

Fourth Embodiment

A structure of an upper electrode 18 d of one sub-pixel in the liquidcrystal display panel 10D in the fourth embodiment will be explainedwith reference to FIGS. 7A and 7B. In FIGS. 7A and 7B, the samereference numerals and signs are given to the components as the liquidcrystal display panel 10A according to the first embodiment and thedetailed explanation thereof is omitted. The upper electrode 18 dincludes plural pairs of slits 17 d 1, 17 d 2, in which slits in eachpair have the same shape and arranged to be inverted with respect toeach other. The slit 17 d 1 as one of the slits has the same shape asthe slit 17 a of the liquid crystal display panel 10A of the firstembodiment, whereas the other slit 17 d 2 has a structure in which theslit 17 d 1 is inverted in the vertical direction at a central axis Xdin the direction orthogonal to the longitudinal direction of the slit,for example, in FIG. 7B.

When the above structure is applied, many pairs of slits 17 dl, 17 d 2having different shapes from each other can be arranged symmetricallywith respect to the central axis Xd within one sub-pixel. Additionally,many slits can be arranged within one sub-pixel, and a light emittingstate of liquid crystal will be symmetrical with respect to the centralaxis Xd in the direction orthogonal to the longitudinal direction of theslits 17 d 1, 17 d 2. According to the liquid crystal display 10D of thefourth embodiment, viewing-angle characteristics become good as well asthe transmittance is improved, thereby realizing the liquid crystaldisplay panel having good display quality and less coloring.

Fifth Embodiment

A structure of an upper electrode 18 e of one sub-pixel in the liquidcrystal display panel 10E in the fifth embodiment will be explained withreference to FIGS. 8A and 8B. In FIGS. 8A and 8B, the same referencenumerals and signs are given to the same components as the liquidcrystal display panel 10D according to the fourth embodiment and thedetailed explanation thereof is omitted. The upper electrode 18 eincludes plural pairs of slits 17 e 1, 17 e 2, in which slits in eachpair have different shapes from each other. The slit 17 e 1 as one ofthe slits has the same shape as the slit 17 c of the liquid crystaldisplay 10C of the third embodiment, however, the other slit 17 e 2 isformed so that a left long edge 33′ and a right long side 34′ areparallel to the right long edge 34 and the left long edge 33 of one slit17 e 1 respectively.

In the above structure, the slits have shapes which are commonly calledcomplementary shapes. The slits 17 e 1, 17 e 2 are asymmetrical withrespect to a central axis Xe in the direction orthogonal to thelongitudinal direction of the slits, and many slits 17 e 1, 17 e 2 canbe arranged in each one sub-pixel. Moreover, the slits can cross therubbing direction with at least three angles of θ1 to θ3 in each pair ofslits as shown in FIG. 8B. As a result, the liquid crystal display panel10E will have three VT characteristics of θ1 to θ3 as shown in FIG. 9,which is observed by an observer as the penal which has the VTcharacteristics represented by an envelope of three VT characteristics.For example, when the long edges 33, 34 and the long edges 33′, 34′forming the slits 17 e 1, 17 e 2 are not formed to be parallel in thesame slit respectively, angles made by the long edges 33, 34 as well asthe long edges 33′, 34′ and the rubbing direction R will have four VTcharacteristics of θ1 to θ4. If a tinge of yellow is added in respectiveVT characteristics, the color is compensated with one another inrespective characteristics such that, when some region has a tinge ofyellow, yellow does not appear in other regions of VT characteristics,as a result, coloring phenomenon can be more suppressed.

The slits according to the embodiments have shapes in which widths ofboth ends of slits are different. When applying the structure, the VTcharacteristics vary according to the width difference, therefore,plural VT characteristics can be obtained not only by angles made by therubbing angle but also by the slit width, which enables of the reductionof coloring with each other and suppression of the coloring phenomenon.As a result, the high-quality liquid crystal display panel can beprovided.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The application is claimed as follows:
 1. A liquid crystal display panelcomprising: a pair of substrates arranged face to face so as to sandwicha liquid crystal layer; a lower electrode formed on one of the pair ofsubstrates; an upper electrode formed on a surface of a lower substratethrough an insulating layer, in which plural slits are formed in eachsub-pixel; and an alignment film formed so as to cover a surface of theupper electrode and the insulating layer, wherein the plural slits havedifferent widths at both ends of the slits in a longitudinal direction.